It is normal for some heat to be dissipated by electronic components during use. However, excess heat can be damaging to the electronic components or to the devices in which they are incorporated. It is therefore important to control heat generated by electronic components and to provide adequate cooling to ensure reliable and safe operation of those components.
It is common to use air to cool electronic components. For example, device casings or cabinets which house electronic components can include air cooling devices such as fans. They may also include mechanical features such as ducts or baffles to enable and enhance air flow around the electronic components. This controls the temperature of the electronic components, because heat is convected away by the air.
However, if it is not properly managed, cooling electronic components using air distribution can lead to problems. For example, the air may be contaminated by dust. A product may be installed in an environment which is heavily contaminated by fine dust such as in a paper, textile or ceramic plant. Such dust settling on exposed electronic components and printed circuit boards (PCB's) can interfere with the normal operation of those components and PCB's. Amongst other things, it can result in a reduction in electrical isolation between areas of high electrical potential, and thus may pose a serious safety risk.
In addition, air used to cool electronic components may be contaminated by gases which are corrosive or otherwise harmful to electronic components and PCB's. If a product is used in a polluted environment where such corrosive gases are present, and if it cooled using a fan or other means to blow air through the electronics, the corrosive gas pollution will be drawn into the product and over the electronic components. Areas where there is more air flow will be exposed to a greater level of this pollution. Therefore areas which have a high density of electrical components and thus require significant cooling could be exposed to significant amounts of corrosive gases, which would impair their operation, thus making them less efficient and potentially creating a safety risk.
One known approach for protecting electronic components and PCB's from contaminants such as dust pollution and corrosive gases in cooling air is known as conformal coating. This approach involves applying a coating directly to electronic circuitry to protect it against dust, gases, chemicals, or moisture in air that could affect the performance of the electronic circuitry. Conformal coating can also be used to protect the electronic circuitry from high temperatures that could cause the electronics to be damaged or even to fail completely. Conformal coating can be done by dipping, spraying or brushing the electronic circuits with a suitable material which might be for example a solvent based acrylic. It is possible to selectively conformal or coat particular areas of electronic circuitry within a device, for example in regions where exposure to contaminated air is more likely and/or where there are more likely to be temperature extremes.
It is not always practical to use conformal coating for electronic circuitry. In addition, the process of conformal coating adds to the cost of manufacture and also the time taken to produce electronic circuits for use in devices that make use of air cooling.
No known approach provides reliable protection of electronic circuitry from potential contaminants within cooling air in an efficient, reliable and cost effective manner.